Showing papers by "University of Tübingen published in 1988"

Dissociation of the lateral and medial cerebellum in movement timing and movement execution.

Abstract: In a previous study (Ivry and Keele, in press), cerebellar patients were found to be impaired on both a motor and a perceptual task which required accurate timing. This report presents case study analyses of seven patients with focal lesions in the cerebellum. The lesions were predominantly in the lateral, hemispheric regions for four of the patients. For the remaining three patients, the lesions were centered near the medial zone of the cerebellum. The clinical evaluation of the patients also was in agreement with the different lesion foci: lateral lesions primarily impaired fine motor coordination, especially apparent in movements with the distal extremities and medial lesions primarily disturbed balance and gait. All of the patients were found to have increased variability in performing rhythmic tapping when tapping with an effector (finger or foot) ipsilateral to the lesion in comparison to their performance with a contralateral effector. Separable estimates of a central timekeeper component and an implementation component were derived from the total variability scores following a model developed by Wing and Kristofferson (1973). This analysis indicated that the poor performance of patients with lateral lesions can be attributed to a deficit in the central timing process. In contrast, patients with medial lesions are able to accurately determine when to make a response, but are unable to implement the response at the desired time. A similar dissociation between the lateral and medial regions has been observed on a time perception task in patients with cerebellar atrophy. It is concluded that the lateral regions of the cerebellum are critical for the accurate functioning of an internal timing system.

Effect of Ca2+ on cross-bridge turnover kinetics in skinned single rabbit psoas fibers: implications for regulation of muscle contraction

Abstract: The effect of Ca2+ upon the rate constant of force redevelopment following a period of isotonic shortening with immediate restretch to the starting sarcomere length was studied in rabbit psoas fibers at 5 degrees C. Control experiments support the assumption that the rate constant of force redevelopment represents isometric cross-bridge turnover kinetics (fapp + gapp), where fapp and gapp are the rate constants characterizing the transitions from the non-force-generating states to the force-generating states and back to the non-force-generating states, respectively. Parallel measurements of the rate constant of force redevelopment and of force, stiffness, and fiber ATPase during isometric contraction allow the effect of Ca2+ upon fapp and gapp to be determined. Analysis reveals that Ca2+ has a marked effect upon fapp, while gapp remains approximately unchanged. Furthermore, in the range above 25-30% of maximum Ca2+ activation, regulation of force, stiffness, and ATPase is mediated through changes in fapp. Below this range, however, it cannot be ruled out that, in addition, cross-bridges are also switched in and out of the turnover process ("recruitment"). As a consequence of regulation through turnover kinetics, both Ca2+ sensitivity and the slope of force-pCa (-log[Ca2+]) relations are shown to be affected by the ratio fapp/gapp, which may represent an important mechanism of modulation of contractile function in addition to modulation through changes within the regulatory protein system.

Prepeptide sequence of epidermin, a ribosomally synthesized antibiotic with four sulphide-rings

Abstract: The genetic basis for the biosynthesis of large polypeptide antibiotics such as nisin has not been explained so far. We show here that the structural gene epiA encoding the antibiotic epidermin from Staphylococcus epidermidis is located on a 54-kilobase plasmid and codes for a 52-amino-acid prepeptide, which is processed to the tetracyclic 21-peptide amide antibiotic. The mature sequence of epidermin corresponds to the C-terminal 22-peptide segment of pre-epidermin and contains the precursor amino acids Ser, Thr and Cys, from which the unusual amino-acid constituents are derived. The more lipophilic epidermin is cleaved at a hydrophilic turn between Arg-1 and Ile+1 from the N-terminal segment-30 to -1, which probably assumes a partially amphiphilic alpha-helix conformation. We propose that the N-terminus (-30 to -1) plays a cooperative role during modification reactions and prevents toxicity of the mature epidermin to the producing strain before the antibiotic is cleaved off and secreted.

Transcranial Doppler ultrasonography in raised intracranial pressure and in intracranial circulatory arrest.

Abstract: Transcranial Doppler ultrasonography was used to monitor 71 patients suffering from intracranial hypertension with subsequent brain death Among these, 29 patients were also assessed for systemic arterial pressure and epidural intracranial pressure, so that a correlation between cerebral perfusion pressure and the Doppler ultrasonography waveforms could be established Four-vessel angiography was also performed in 33 patients after clinical brain death With increasing intracranial pressure, the transcranial Doppler ultrasonography waveforms exhibited different characteristic high-resistance profiles with first low, then zero, and then reversed diastolic flow velocities, depending on the relationship between intracranial pressure and blood pressure (that is, cerebral perfusion pressure) This study shows that transcranial Doppler ultrasonography may be used to assess the degree of intracranial hypertension This technique further provides a practicable, noninvasive bedside monitor of therapeutic measures

Gallidermin: a new lanthionine-containing polypeptide antibiotic.

Abstract: Gallidermin is a new member of the class of lanthionine-containing peptide antibiotics, which are summarized under the common name lantibiotics. The lantibiotic gallidermin is produced by Staphylococcus gallinarum (F16/P57) Tu3928, and it exhibits activities against the Propionibacteria, involved in acne disease. Gallidermin differs from the recently discovered tetracyclic 21-residue peptide antibiotic epidermin only in a Leu/Ile exchange in position 6. The isolation procedures for gallidermin included adsorption directly from the culture broth, ion-exchange chromatography of the amphiphilic and basic polypeptide followed by desalting, and final purification by reversed-phase HPLC. The structural elucidation of the polypeptide containing four thioether bridges involved mainly a combination of automated gas-phase sequencing, thermospray liquid chromatography/mass spectrometry and fast-atom-bombardment mass spectrometry.

Divergent projections of physiologically characterized rat ventral cochlear nucleus neurons as shown by intra-axonal injection of horseradish peroxidase.

Abstract: An attempt was made to correlate electrophysiological and morphological characteristics of rat ventral cochlear nucleus neurons. Their axonal course and their soma morphology were investigated using the intra-axonal horseradish peroxidase method. Prior to labeling, neurons were characterized by recording their response patterns to acoustic stimulation with pure tones. Three types of cells were found: Category I (37 neurons) exhibited “primarylike” responses and a spontaneous firing rate below 10 spikes/s. Category II (21 neurons) showed “on” responses and little spontaneous activity. Category III (9 neurons) had “primarylike” responses like neurons in category I. However, the spontaneous activity rate of these neurons was significantly higher (mean: 95 spikes/s). Among the response categories, the morphological characteristics differed in some prominent aspects. Within each category, however, the morphological properties were rather similar. All neurons in category I were globular/bushy cells located in the area of the entrance of the cochlear nerve. The axon of each cell coursed along the ventral acoustic stria and consistently innervated the lateral superior olive ipsilaterally, and the nucleus of the trapezoid body and the nucleus of the lateral lemniscus contralaterally. Some neurons also projected to periolivary nuclei ipsilaterally and contralaterally. Neurons in category II were located in the posteroventral cochlear nucleus and were presumably multipolar/stellate cells. Their axons coursed via the intermediate acoustic stria and innervated mainly contralateral periolivary regions as well as the contralateral nucleus of the lateral lemniscus. Ipsilaterally, the lateral superior olive and the superior periolivary nucleus were innervated by some of the category II neurons. Somata types of neurons in category III could not be identified morphologically, but somata were located in caudal parts of the posteroventral cochlear nucleus that correspond to the octopus cell area. Their axons coursed via the intermediate acoustic stria and innervated periolivary regions and the contralateral nucleus of the lateral lemniscus. Thus, their axonal distribution differed only slightly from neurons in category II. These data confirm and extend previous findings regarding the efferent connections of ventral cochlear neurons. They emphasize the complexity of the axonal projection patterns of single cochlear nucleus cells. Since two types of response patterns and three types of axonal projection patterns have been observed, there remains an ambiguous relation between response pattern and axonal projection site. It is concluded that the response pattern to pure tone stimulation alone is not sufficient to describe physiological characteristics allowing for the establishment of structure-function relations. Only if one considers additional physiological properties like the spontaneous activity rate and the shape of tuning curves, does a correspondence between structure and function become apparent.

Chronic back pain and rheumatoid arthritis: predicting pain and disability from cognitive variables.

Abstract: Cognitive-behavioral models of chronic pain emphasize the importance of situation specific as well as more general cognitive variables as mediators of emotional and behavioral reactions to nociceptive sensations and physical impairment. The relationship of situation-specific pain-related self-statements, convictions of personal control, pain severity, and disability levels was assessed in samples of chronic back pain and rheumatoid arthritis patients. Both the more general and the situation-specific sets of cognitive variables were more highly related to pain and disability than disease-related variables. This association was found in the back pain patients who displayed only marginal levels of organic findings as well as the rheumatoid arthritis sample who had a documented basis for their pain. The combination of both situation-specific and general cognitive variables explained between 32 and 60% of the variance in pain and disability, respectively. The addition of disease-related variables improved the predictions only marginally. These results lend support to the importance of cognitive factors in chronic pain syndromes.

Epidemiological models for sexually transmitted diseases

Abstract: The classical models for sexually transmitted infections assume homogeneous mixing either between all males and females or between certain subgroups of males and females with heterogeneous contact rates. This implies that everybody is all the time at risk of acquiring an infection. These models ignore the fact that the formation of a pair of two susceptibles renders them in a sense temporarily immune to infection as long as the partners do not separate and have no contacts with other partners. The present paper takes into account the phenomenon of pair formation by introducing explicitly a pairing rate and a separation rate. The infection transmission dynamics depends on the contact rate within a pair and the duration of a partnership. It turns out that endemic equilibria can only exist if the separation rate is sufficiently large in order to ensure the necessary number of sexual partners. The classical models are recovered if one lets the separation rate tend to infinity.

Restoration of masticatory function by microsurgically revascularized iliac crest bone grafts using enosseous implants.

Abstract: Forty-one free osteomyocutaneous groin flaps were used for osteoplastic reconstruction of the mandible (n = 36) or maxilla (n = 5) following tumor resection or, less often, chronic osteomyelitis or traumatic bone loss. Nineteen grafts were transplanted into a preirradiated area. No total loss of a transplant or pseudoarthrosis was observed. Plates were used for graft fixation. Free grafting was necessary in two patients, who developed partial bone loss because of infection. Four patients showed partial loss of the skin part of the myocutaneous flap. Improvement of the preprosthetic situation was achieved by a total of 38 enosseous aluminium oxide implants into the vascularized bone grafts. All showed primary healing and successful integration in prosthetic rehabilitation, maximum follow-up time being 30 months.

Control of isometric finger force in patients with cerebellar disease.

Abstract: Control of isometric forces during grasping or handling of objects is an essential feature of all skilled manual performances. Previous studies of hand function in cerebellar patients were restricted to movements; force control was only investigated under isotonic conditions in combination with movements. Control of isometric forces during voluntary contraction of finger muscles was investigated in 31 patients with chronic cerebellar disease and in 20 normal controls. Eight patients with Friedreich's ataxia were considered to be typical for a disease affecting the afferents to the cerebellum; 4 patients with anterior lobe atrophy, which affects leg movements to a greater extent than finger movements, were compared with 3 patients with hemisphere lesions; 16 patients suffered from diffuse cerebellar atrophy. Using a recently developed microcomputer system for the continuous measurement of finger force, control of isometric force was studied in several tasks within the same subjects. The tasks included the maintenance of constant force output at different force levels with and without visual feedback, fast repetitive force changes, tracking of a sinusoidal target presented visually, and measurement of maximum grip force. The amount of voluntary contraction in terms of muscular power was normal in all patients; in all other tasks clear deficits were observed. The extent of the disturbances was highly variable between patients even within the same clinical subgroup. The detailed analysis of force traces revealed a great variety in types of disturbance. The frequently observed slowing of the speed in repetitive force changes can be attributed to different components in different patients and not only to difficulties at turning points as might be predicted from comparable movement studies. In addition, performance deficits across different tasks were not uniform, indicating dissociation of impairment. Deficits in maintaining force, which may be interpreted as dysmetria or due to tremor, do not necessarily imply an abnormality in diadochokinesis, as measured in fast repetitive force changes, nor does the converse apply.

On the role of vestibular, visual and somatosensory information for dynamic postural control in humans.

Abstract: Postural stabilization in altered visual, vestibular, and somatosensory conditions was investigated in humans subjected to either a fast unidirectional displacement or to a continuous sinusoidal movement of the standing support. Visual inputs were varied in four ways: (1)stroboscopic illumination, (2)stabilizing the visual surround with respect to head movements, (3)inducing apparent body movement in pitch using stripe patterns which moved continuously up or down in front of the subject, (4)eye closure. Static vestibular (and neck) input was modified by bending the head forwards or backwards, or to the right or left shoulder with the eyes closed. Somatosensory input from both feet was reduced by an ischaemic block at a level just above the ankle joints. With fast, transient, toe-up platform displacements (high-frequency test) neither the biomechanical parameters as measured by the displacement of the centre of foot pressure nor the early EMG responses of the anterior tibial and triceps surae muscles were modified by a manipulation of visual, vestibular or somatosensory feedback conditions. Sudden disturbances are obviously compensated by an early set of reflex-like muscle responses that, depending on the starting position, are stereotypically released without feedback control to save time at the expence of accuracy (emergency reaction). Continuous regulation of upright stance during sinusoidal displacement at 1 or 0.3 Hz (low-frequency test), however, clearly depends on visual, vestibular, and somatosensory feedback. Studies in patients should contain both tests, since each examines different functions of the very complex posture stabilizing network. Manipulations of sensory feedback, however, are only recommended in the low-frequency test. The experimental suppression or disturbance by disease of two of the three feedback loops invariably causes a conspicuous postural instability.

Genetics of the iron dicitrate transport system of Escherichia coli.

Abstract: Escherichia coli B and K-12 express a citrate-dependent iron(III) transport system for which three structural genes and their arrangement and products have been determined. The fecA gene of E. coli B consists of 2,322 nucleotides and encodes a polypeptide containing a signal sequence of 33 amino acids. The cleavage site was determined by amino acid sequence analysis of the unprocessed protein and the mature protein. For the processed form a length of 741 amino acids was calculated. The mature FecA protein in the outer membrane contains at the N terminus the "TonB box," a pentapeptide, which has hitherto been found in all receptors and colicins which functionally require the TonB protein. In addition, the dyad repeat sequence GAAAATAATTCTTATTTCG is proposed to serve as the binding site of the Fur iron repressor protein. The fecB gene was mapped downstream of fecA and encodes a protein with an apparent molecular weight of 30,000. It was synthesized as a precursor, and the mature form was found in the periplasm. The fecD gene follows fecB and was related to a membrane-bound protein with an apparent molecular weight of 28,000. In Mu d1 insertion mutants upstream of fecA, the fec genes were not inducible by iron limitation and citrate, indicating a regulatory region, termed fecI, which controls fec gene expression.

The consequences of brood size for breeding blue tits. iii. measuring the cost of reproduction: survival, future fecundity, and differential dispersal.

Abstract: To determine how the cost of reproduction varies with brood size, a population of blue tits (Parus caeruleus) breeding in Wytham Wood, England, was manipulated over a three year period. Two hundred sixteen pairs were randomly assigned 3, 6, 9, 12, or 15 nestlings; nestlings were exchanged soon after hatching. Survival of adult females (as measured by the proportion recaptured in the following winter and/or spring) declined significantly with increasing brood size in two out of three years; there was significant year-to-year variation in the relationship of recapture rate to brood size. Mean female recapture rates (averaged over the three years) declined in a linear fashion (P < 0.01). There was no significant linear or curvilinear relationship between male-recapture rate and brood size in any of the three years nor was there a significant linear or curvilinear relationship for the data averaged over the three years. Nevertheless, recapture proportions for males differed significantly with respect to brood size (χ2 test, P < 0.05). The possibility that experimental brood size influences subsequent dispersal (and therefore biases measures of survival based on recapture rates to differing degrees) was examined by comparing distances moved by breeding adults from one year to the next. There was no relationship between brood size and dispersal distance within the study area for either sex, except that females given broods of three were significantly more likely to move more than 300 m than were those given broods of 6-15 young. Both males and females showed evidence of a cost with respect to future fecundity: as brood size increased, the number of surviving offspring produced in the following year decreased from 1.5-1.6 (for adults that had reared 3-6 young) to 0.4 (for those that had reared 15 young). The relationship of future reproductive success to experimental brood size did not differ among years or between the sexes. The number of eggs laid and number of young hatched in year n + 1 did not differ significantly with respect to brood size in year n; rather, differences in future fecundity reflected differences in the survival prospects of young reared in year n + 1.

Structural changes in vesicle membranes and mixed micelles of various lipid compositions after binding of different bile salts

Abstract: Binding equilibria of common bile salts (BS) and different mixtures of membrane lipids were correlated with BS-induced structural changes of large unilamellar vesicles, with transition of vesicles to mixed micelles (MM), and with successive transformations of MM. At very low BS concentrations, in the outer vesicle monolayer definite BS/lipid aggregates are formed, the size and BS binding strength of which depend on the BS and lipid species involved. At increasing BS concentrations, binding to the membranes is hampered, and above a critical BS content, membrane stress due to asymmetric BS binding leads to formation of transient membrane holes, as shown by inulin release from the vesicles. Independent of the BS and lipid species, membrane solubilization starts at a ratio r = 0.3 of bound BS/lipid. Increasing phosphatidylserine, phosphatidylethanolamine, and cholesterol contents stabilize the lecithin membrane against BS to different degrees and in different ways, whereas the destabilization by sphingomyelin is probably due to the enhancement of the membrane gel-liquid transition temperature. Conjugation of the BS with glycine or taurine has a modulating effect on membrane hole formation, rather than on lipid solubilization. Diphenylhexatriene fluorescence anisotropy indicates a BS-induced drop of the internal membrane order and its restoration during membrane solubilization. At higher concentrations ursodeoxycholate induces additional condensation, whereas the other BS cause internal disorder in the MM. Above ratios r of approximately 8:1, we found a release of BS from these MM and suggest a rodlike structure for them. The results were discussed with respect to BS/membrane interactions during lipid excretion from the liver cell.

On the transmission dynamics of HIV

Abstract: The classical models for sexually transmitted disease implicity assume that all contacts with the same partner are concentrated in one instant. A new model is presented which takes into account the duration of a partnership and the number of contacts with the same partner. An explicit formula is given for the number of partners during a lifetime which is necessary to maintain the infection at an endemic level. The present basic model may serve as a building block in more realistic models for the spread of HIV in the population.

Molecular characterization of the hemolysin determinant of Serratia marcescens.

Abstract: The nucleotide sequence of a 7.3-kilobase-pair fragment of DNA encoding a hemolytic activity from Serratia marcescens was determined. Two large open reading frames were identified, designated shlA (Serratia hemolysin) and shlB, capable of encoding polypeptides of 165, 056 and 61,897 molecular weight, respectively. Both reading frames were expressed in vivo. The shlB gene product was localized to the outer membrane of Escherichia coli cells harboring the S. marcescens hemolysin determinant. Consistent with this location, a signallike sequence was identified at the N terminus of the polypeptide predicted from the nucleotide sequence of the shlB gene. Hyperexpression of the shlB locus permitted the identification of two shlB-encoded polypeptides of 65,000 and 62,000 molecular weight, respectively. Determination of the N-terminal amino acid sequence of the purified 62,000-molecular-weight protein confirmed that it was the mature form of the ShlB protein initially synthesized as a precursor (65,000-molecular-weight protein). By using polyclonal antisera raised against the purified proteins, ShlA and ShlB were identified in the outer membrane of S. marcescens. The shlA gene product was shown to interact with erythrocyte membranes, confirming it as the hemolysin proper. Both hemolysis and the interaction of ShlA with erythrocyte membranes did, however, require the ShlB function. Progressive deletion of the C terminus of the ShlA protein gradually reduced hemolytic activity until 37% of the amino acids had been removed. Elimination of 54% of the amino acids produced a nonhemolytic protein which, however, was still capable of associating with erythrocyte membranes.

Models for pair formation in bisexual populations.

Abstract: Birth, death, pair formation, and separation are described by a system of three nonlinear homogeneous ordinary differential equations. The qualitative properties of the system are investigated, in particular the conditions for existence and global stability of the bisexual state.

Fast algorithms for multiple evaluations of the riemann zeta function

Abstract: The best previously know algorithm for evaluating the Riemann zeta function, ζ(σ+it), with σ bounded and t large to moderate accuracy was based on the Rienmann-Siegel formula and required on the order of t 1/2 operations for each value that was computed. New algorithms are presented in this paper which enable one to compute any single value of ζ(σ+it) with σ fixed and T≤t≤T+T 1/2 in O(te) operations on numbers of O(log t) bits for any e>0 for example. These algorithms lead to methods for numerically verifying the Riemann hypothesis for the first n zeros in what is expected to be O(n 1+ e) operations

The hole concentration on oxygen sites in the highT c superconductor Y1−Ba2−Cu3−O7−x

Abstract: From XPS core level spectroscopy the average copper charge on the Cu sites in the high temperature superconductor Y1Ba2Cu3O7−x is determined as function of the oxygen vacancy concentrationx. Analysis of these data leads to the suggestion that there are holes on the oxygen sites in the basal plane of the crystal structure. The probability for holes on these oxygen ions is rather constant for 0≦x≦0.3 with a value of 0.64 and decreases to zero forx=0.5. The dependence of the superconducting transition temperature on the hole concentration is discussed. An energy level diagram for Cu2+ and Cu3+ in YBa2Cu3O7−x is constructed.

Baroreceptor Stimulation Alters Pain Sensation Depending on Tonic Blood Pressure

Abstract: It has been hypothesized that activation of the baroreceptor reflex arc, by its central nervous inhibitory effects, is involved in an operant learning mechanism of blood pressure elevation. The present study investigated the effects of mechanical stimulation of the baroreceptors in the carotid sinus on pain threshold and electrical brain activity in two groups of humans with different tonic blood pressure levels. In normotensives, baroreceptor stimulation lowered pain threshold as compared to a control condition, while borderline hypertensives tolerated more intense electric stimulation when baroreceptors were activated. A marked reduction of the contingent negative variation in anticipation of the aversive stimulation accompanied baroreceptor stimulation, probably a consequence of baroreceptor afferent impulses exerted via brainstem centers to cerebral cortex. The distribution of the potential change across the scalp depended on the tonic blood pressure, indicating differences in brain functioning between normotensives and borderline hypertensives. The present results suggest that the hypothesis of an operantly-conditioned blood pressure elevation under stress may be valid only in subjects with a predisposition for essential hypertension.

Individual and Situational Differences in Recovery from Bereavement: A Risk Group Identified

Abstract: The Tubingen Longitudinal Study of Bereavement was designed to provide information on (a) health deterioration and recovery following bereavement, (b) risk factors in bereavement, and (c) selection and social desirability as potential biases in health findings in this type of research. A sample of widows and widowers were interviewed three times during the first two years following their loss. Measures of their health and well-being were compared to those of a matched sample of married individuals. Data were also collected on the health status of some of the widowed who refused participation. The findings suggest the following conclusions: (1) Partner loss is associated with an increased level of depressive and somatic symptoms during the first six months, but the majority of bereaved gradually recover over the two-year period. (2) Individuals with low internal control beliefs who have experienced an unexpected loss constitute a risk group of individuals who suffer most and recover least. (3) Due to selection, the impact of bereavement is likely to be underestimated for widowers and overestimated for widows. Implications of these findings are discussed.

Reversible brain shrinkage in abstinent alcoholics, measured by MRI.

Abstract: Magnetic resonance imaging of the intracranial CSF volume was compared before and after 5 weeks of confirmed abstinence in 9 alcohol-dependent patients. All patients showed a highly significant reduction in CSF volume in accordance with reexpansion of the brain after alcohol abstinence. T2 values for white matter, estimated by linear regression from 16 echoes of a CPGM sequence, however, showed no significant increase such as occurs in rehydration. This indicates, that alcohol-induced reversible brain atrophy cannot be attributed to fluctuation of free water in the brain only.

Species-specific DNA sequences for identification of somatic hybrids between Lycopersicon esculentum and Solanum acaule

Abstract: Species-specific highly repeated DNA sequences can be used to screen the progeny of protoplast fusions combining different species. Such probes are easy to clone and can be detected by fast methods, e.g., hybridization to total genomic DNA. Furthermore, due to their high copy number, hybridization signals are strong and represent more than one locus, unlike isozymes or resistance markers. After cloning and screening for species-specific DNA sequences we characterized the highly repeated DNA sequences of the solanaceous species Solanum acaule and Lycopersicon esculentum var. “gilva”. DNA sequencing and hy ridization revealed a prominent, tandemly arranged satellite DNA repeat of 162 bp in Lycopersicon esculentum and a different satellite repeat of 183 bp, also tandemly organized, in Solanum acaule. Each repeat is absent in the respective other species. Therefore, we have used these DNA repeats as markers to distinguish regenerated interspecific somatic hybrids from the respective fusion partners. These hybrids were clearly identified by Southern hybridization and dot-blot assays to the respective 32P-labelled satellite DNA.

Sturm-Liouville eigenvalue problems on networks

Abstract: The description of heat conduction on ramified wires, for instance, leads to a Sturm-Liouville eigenvalue problem on a network. It is shown that these problems are special canonical eigenvalue problems in the sense of Holder, and therefore they can be investigated within the theory of S-Hermitian eigenvalue problems. In particular, Wielandt's expansion theorem can be applied in order to obtain eigenfunction expansions.